COMPOSITION BASED ON CERIUM OXIDE AND ZIRCONIUM OXIDE HAVING HIGH REDUCIBILITY AND HIGH SPECIFIC SURFACE, METHOD FOR PREPARATION THEREOF AND USE THEREOF AS CATALYST

摘要

PROBLEM TO BE SOLVED: To provide a composition which is suitable for the treatment of exhaust gas from an internal-combustion engine and has high reducibility and a high specific surface area.

SOLUTION: A method for the preparation of the composition comprises the following steps: (a) a mixture containing a cerium compound, a zirconium compound and optionally an element of the lanthanide series elements except cerium is formed; (b) the mixture is brought into contact with a basic compound to form a precipitate; (c) the precipitate is heated in an aqueous medium; (d) an additive selected from anionic surfactants, nonionic surfactants, polyethylene glycols, carboxylic acids and their salts and surfactants obtained by ethoxylating carboxymethylated fatty alcohols is first added to the resulting aqueous medium and optionally the precipitate is subsequently separated or (d') the precipitate is first separated and the additive is subsequently added to the separated precipitate; (e) the additive-added precipitate is milled; (f) the milled precipitate is calcined under an inert gas or under vacuum, in a first stage, at a temperature of at least 850°C and then under an oxidizing atmosphere, in a second stage, at a temperature of at least 400°C to prepare the composition having the reducibility of at least 70% and the specific surface area of at least 15 m2/g.

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